Why compress WebP
WebP is a web-first format: it is lighter than JPG at the same quality, which is exactly why large sites store their graphics in it. But a WebP file can still be heavy: exports from design tools are often saved "with headroom", and a batch of images on a site adds up to hundreds of megabytes of traffic.
Compressing WebP re-encodes the file with a more thorough encoder: same format, same picture to the eye - fewer bytes. The quality slider picks the balance, from a barely noticeable reduction to maximum savings for thumbnails.
How compression works
The file is decoded to pixels and written again with the encoder at maximum effort: more variants of splitting the picture into blocks and describing each block are tried. It is the same work the encoder does when saving - just more careful and slower. The result is written as WebP again: browsers and programs open it exactly like the original.
If the source file was already encoded economically there is nothing left to win - you get the original back with a warning. The service never returns a "compressed" file that weighs the same or more than the input.
What is preserved
- The WebP format and the pixel dimensions of the picture.
- Transparency for files with an alpha channel.
- The color profile: hues stay where they were.
Who needs this
Website owners - every hundred kilobytes makes a page faster on mobile connections and improves search rankings. Webmasters with image-heavy catalogs - a thousand product pictures lose gigabytes after re-encoding generous exports. Theme and template authors - shipped graphics should not bloat the package.
How to pick the quality
For product cards, banners and article illustrations the standard is mid slider values: weight drops by a quarter to a third while the difference from the original is invisible. Icons and small graphics allow more economical values: at a couple hundred pixels compression artifacts are unreadable. For covers and large images viewed up close, take higher quality - their weight is small relative to the page anyway.
Watch the batch, not a single file: 50 kilobytes saved per picture in a thousand-item catalog means tens of megabytes on every category load. It is the batch saving, not a heroic fight over one file, that makes a site fast.
Why a file may not shrink
If the image was already encoded economically, re-encoding brings no gain. The service returns the original file with a warning - you will not get a "compressed" file of the same weight.
What is WEBP to WEBP conversion used for
Optimizing an online store catalog
Hundreds of product cards exported with headroom free up gigabytes of monthly traffic after re-encoding.
Making pages faster
WebP was chosen for speed - finish the job: every hundred kilobytes saved shortens load time on mobile.
Hosting and backups
Lighter files mean lower storage bills and faster graphics sync between environments.
Tips for converting WEBP to WEBP
Start with medium quality
A value around 80 is the web standard: the weight drops noticeably while the difference from the original is invisible.
Compress from the originals
Keep uncompressed exports and re-encode from them: compressing an already compressed file brings almost no gain.
Compare PNG sources with WebP conversion
If the source is a PNG, after compressing compare the weight with a full WebP conversion: for web graphics a format change often saves more than re-encoding within the format.